Abstract:
In parallel with climate changes, understanding tropical rainfall dynamics becomes crucial
for effective decision-making in agriculture, water management, and disaster
preparedness. Sri Lanka, situated in the tropical Indian Ocean (IO), is particularly
vulnerable to climatic shifts, especially concerning rainfall patterns. Despite this
vulnerability, changes in mean rainfall remain underexplored, highlighting a critical
research gap. The present study addressed this gap by examining shifts in mean
precipitation in a warming climate context. The observational and reanalysis data (1990-
2023) were analyzed to identify a midpoint marking a significant change in rainfall mean
state, using statistical tests and sea surface temperature (SST) trends. This midpoint was
then applied to analyze rainfall and associated climate mechanisms across Sri Lanka. Our
analysis reveals a notable increase in mean rainfall after 2009. The changes in arid, dry,
wet, and intermediate zones were 0.31, 0.74, 0.58, and 0.18 mm day-1 respectively. These
increases are linked with large-scale ocean-atmosphere dynamics, including shifts in wind
patterns, SST, moisture convergence, and vertical wind velocity. Specifically, the rise in
SST in the IO and the resultant circulation patterns have enhanced moisture convergence,
driving the observed rainfall increase from 2009 to 2023 compared to the preceding
period. Our findings provide vital insights for shaping sustainable policies aligned with
SDG 13 on climate action.
